Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization ofH2
| Autor: | Wu, J., Kunitski, M., Pitzer, M., Trinter, F., Schmidt, L.Ph.H., Jahnke, T., Dörner, R., Magrakvelidze, M., Madsen, C.B., Thumm, U., Madsen, L.B. |
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| Rok vydání: | 2013 |
| Předmět: |
Physics
Photoemission spectroscopy Atoms in molecules Binding energy General Physics and Astronomy Electron Photon energy Kinetic energy 7. Clean energy 01 natural sciences 010305 fluids & plasmas Ion Ionization 0103 physical sciences Physics::Atomic and Molecular Clusters Physics::Atomic Physics Atomic physics 010306 general physics |
| Zdroj: | Wu, J, Kunitski, M, Pitzer, M, Trinter, F, Schmidt, L P H, Jahnke, T, Dörner, R, Magrakvelidze, M, Madsen, C B, Thumm, U, Madsen, L B, Thumm, U & Dörner, R 2013, ' Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H 2 ', Physical Review Letters, vol. 111, no. 2, 023002 . https://doi.org/10.1103/PhysRevLett.111.023002 Physical Review Letters |
| ISSN: | 1079-7114 0031-9007 |
| DOI: | 10.1103/physrevlett.111.023002 |
| Popis: | We report experimental observation of the energy sharing between electron and nuclei in abovethreshold multiphoton dissociative ionization of H2 by strong laser fields. The absorbed photon energy is shared between the ejected electron and nuclei in a correlated fashion, resulting in multiple diagonal lines in their joint energy spectrum governed by the energy conservation of all fragment particles. Deposition of the photon energy to atoms and molecules is the primary step of the interactions of radiation with matter. The details of this deposition process, in particular how the photon energy is distributed among the subsystems and various internal degrees of freedom, determine all photon-induced chemical and physical dynamics. For the interaction with a strong laser field, this question of energy deposition gets even richer since it is well established that the energy of more photons than the minimal number required for ionization can be absorbed. For atoms in a strong field, this leads to discrete peaks in the photoelectron spectrum that are spaced by the photon energy and referred to as ‘‘above-threshold ionization’’ (ATI) [1]. For molecules the vibrational, rotational, and dissociative motions of the nuclei provide a sink for the photon energy in addition to the electrons. This has been observed in single-photon dissociative ionization of molecules exposed to synchrotron radiation [2–4], where the photon energy is shared by the freed electrons and the nuclear fragments. For the molecular multiphoton case, rich ATI spectra of the freed electron [5–9], bond-softening-induced molecular dissociative ionization [10–15], and the imaging of internuclear distance using nuclear kinetic energy release spectra [16–19] have been reported. The correlation between the fragment ion and the electron energy has most recently been studied in numerical simulations for H 2 þ [20,21]. A nontrivial sharingof the absorbedphoton energy between the electron and nuclei in multiphoton ionization of molecules was predicted and stimulated us to investigate this problem experimentally. Here, we report the experimental observation of the energy sharing between the emitted electron and nuclei from above-threshold multiphoton dissociative ionization of the simplest molecule H 2 by intense femtosecond laser pulses. Discrete numbers of absorbed photons can be identified by peaked diagonal lines in the joint energy spectrum (JES) of the coincidently measured electron and nuclei [20]. Since there is no direct coupling between the nuclei and the laser field for homonuclear diatomic molecules, the laser first couples to the electrons, and the electrons then couple to the nuclei. The energy taken by the nuclei therefore measures the correlation between the electrons and nuclei. Figure 1 shows a much simplified schematics of the process. By absorbing multiple photons (blue vertical arrows), the H2 molecule emits one electron and a nuclear wavepacket on the � þ (ground) state of H 2 þ is launched. It propagates on the � þ potential curve of H 2 þ .P art of this wavepacket already has sufficient energy to escape (direct pathway), while another part can be promoted to the dissociative � þ potential curve by resonant absorption of one additional photon (one-photon pathway). In the multiphoton picture, the sum of the kinetic energy of the proton (Ep), hydrogen atom (EH), and electron (Ee) after the end of the laser pulse is given by |
| Databáze: | OpenAIRE |
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